Direct correlation between mechanical failure and metallurgical reaction in flip chip solder joints

Flip chip solder bonded Si samples were tested under tensile and shear loading as a function of annealing time at 200 deg C. The solder bump was eutectic SnPb and the underbump thin film metallization was Cu/Cr deposited on oxidized Si. Results showed that the failure mode is interfacial fracture and the fracture strength declines fast with annealing time. The fracture was observed by scanning electric microscopy to occur at the Cu-Sn/Cr interface.